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We just experienced our third episode in three months of the security system locking out the starter. The computer recognizes the keys and adjusts the wheel and seat, but when we turn the key, no starter. There is an initial single click as if the battery is weak (which it isn't), and then nothing. When the key is released the computer starts issuing messages, e.g., check suspension, check security system, check headlamps, etc. My understanding is that those messages and codes are the security system creating chaos to deter theft.

Now what's strange (at least to me) is that there seems to be some kind of "self cure". The first time, we replaced the battery and positive post as it showed some corrosion. It worked fine. The second time, after trying the key several times and then leaving it for an hour while waiting for a tow truck, it started when the gear shift was moved from park to neutral. We thought maybe the problem was in the shift indicator?! The third time, we tried all our tricks by disconnecting the battery for several minutes, moving the shift lever from park to neutral and back, etc. After leaving it overnight, we had it flat bedded 35 miles to the dealer. After rolling it off, the service tech got in and it started right up. It then showed EVERY code except the ABS system.

The dealer says he suspects either the IPcluster or the ECM or both, but isn't really sure and can't guarantee a fix even after these are replaced. (The car has 64K miles). He claims they've checked the grounds and they seem "fine". So...any advice or suggestions other than to spend $1400 for the dealer's "fix"? Thanks!
 

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'02 ETC CE, '04 CTS-V, '04 XLR, '13 XTS Platinum
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Intermittents, whether in an analog or digital circuit are among the most difficult faults to diagnose and repair, and almost always (unfairly) reflect poorly on the technician/dealership in the frustrated eyes of the customer. . Your problem sounds like it falls into this category. While the built-in diagnostics in today's vehicles can be real timesavers, (and as we know too well, time is money) when the codes fail to isolate the root cause of the problem, there are two ways to get it fixed. 1) Educated guessing by replacing the most likely component(s) 2) Down and dirty troubleshooting, which can cost more in labor than the one can bear. Your dealership sounds like they're being realistic with you when they say replacing the suspect components may (or may not) fix the problem. Your best ally is the service manager. You can spend the $1400 and if the problem re-occurs (maybe) he'll take pity on you and throw in some free labor to continue troubleshooting. Then again, being a free market economy, maybe he won't.

So its a tough decision all around. An unreliable car is just as useless as an unreliable gun, only a lot more frustrating (unless you shoot more than drive).
There are several options: Pay the $1400 and pray it works. Have the tech check more than grounds; check every connector and harness that interacts with the data bus. (A big job!) Another alternative: Have the tech connect his diagnostic tools to the bus and cycle the ignition circuit until he can repeat the failure (could take hundreds of tries) and hopefully gather some clues. If they haven't already checked their online GM database for similar occurances in this model of vehicle, that might also be helpful. No matter what they do, you won't know its REALLY fixed unless they can find a definite problem (dirty connector; chaffed wire, plug pin making intermittent contact . . . the list is endless.) or a long period of time goes by without a reoccurance, AFTER they've cashed your check for the new hardware.

A good tech will consult a troubleshooting tree of all the malfunctions that can cause a particular fault (What can trip the theft circuit?) and orient their troubleshooting along those lines. A great tech will consider EVERYTHING that might cause the fault, including thermal, EMI and floating grounds. Good luck with this fault and please post the results here.

CC
 

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1994 Fleetwood 60" Stretch; '07 Avalanche, '95 Nighthawk
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The security system does not create any kind of chaos when it goes into theft deterrent mode. There's no drama - it just lights the SECURITY light and the car won't start. I doubt your problem is related to the security system at all since the starter is getting a blip of juice before it freaks out. The theft deterrent system, when activated, won't allow the starter to turn or the fuel pump to run. I would've voted for the corrosion at the battery but you've already exhausted that possibility.

I doubt the problem is related to any individual module like the PCM. The module with the problem commands the DIC to display a particular message. The EBCM sends ABS codes, the suspension module sends the stability system codes, the PCM sends drivetrain codes, etc. and so on. So, if I had to guess I'd say the IP cluster is freaking out. If he's checked the connections at the IP cluster then he should swap it out with a known good one to see if that fixes it. Of course a dealer won't do that, they'll just charge you for a new cluster (very expensive) and see if that works. If it doesn't, tough luck.

If I were you I'd pick up a used cluster from a salvage yard (www.junkyarddog.com or www.schramauto.com). If it doesn't fix it you'd be no worse off than if the dealer had installed it but it will cost you half as much. They are easy to install and are interchangeable betwen a DTS and a base Deville (if you wanted to upgrade to analog). The only downside with a junkyard unit is the mileage will be off. Last I checked the manufacturer gets $250 to reprogram them (with proof of mileage) - the dealer can't do it.

EDIT: Now that I think about it, the only problem with the IP cluster theory is that it has nothing to do with a no-start situation. That could point to the PCM but, again, I doubt it. If you think the anti-theft system is really kicking in they should replace the anti-theft module first (it's like $75 I think). It doesn't explain the random codes, but they should be replacing the cheap stuff first, not go right for an expensive PCM and cluster.

Good luck!

Jim
 

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all of your problems seem to be ground related, pcm, abs, etc!, there is only 1 body to engine ground and this strap is connected to the alternator bracket try cleaning this at the engine and frame
 
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